Chapter 13 - The Origin of Human Milk Bacteria

Abstract

In the past years, it has become evident that human milk is a source of bacteria to the infant's gastrointestinal (GI) tract; however, the origin of the bacteria present in human milk remains largely unknown. There are a wide variety of sources (skin, mouth, pumps used for milk expression, breast accessories, water used to rinse them, and so on) that, theoretically, can contribute to the composition of the human milk microbiota through direct contact with this biological fluid or with the mammary structures. However, the opposite may also be true: human milk can be a source of bacteria to any bodily location or surface. In addition, some studies suggest that certain bacteria from the maternal GI tract, including the oral cavity, may translocate through a mechanism involving mononuclear immune cells, migrate to the mammary glands via an endogenous cellular route (the bacterial enteromammary pathway), and, subsequently, colonize the GI tract of the breastfed neonate. If such findings are confirmed in the future, we could exert a positive influence on infant health by modulating the maternal oral and GI microbiota.